The long term objective of the proposed research is to qualify and quantify the effects of learning on the functional organization of the adult cortex. We propose to reach this objective by undertaking studies which utilize the technique of in-vivo high-resolution optical imaging of intrinsic signals in conjunction with simultaneous, multiple, single- unit recording. The imaging technique will enable us to follow learning induced changes during and after learning from a global perspective while the unit recording will enable us to probe the cellular basis of learning induced changes from the functional network perspective. The study will be performed in the 'barrel cortex' division of the somatosensory cortex of rewarded and non-rewarded rats in order to quantify the changes induced by rewarded learning. While following and quantifying organizational changes over time we will seek evidence for the hypothesis that these changes originate within the cortex and that such changes involve 'unmasking' of existing changes. Successful completion of the proposed research will expand our understanding about the underlying mechanisms of neuronal organization and their possible modification by external factors. Understanding such mechanisms and their dynamics is important for both the healthy and the diseased brain.